Compact Cabins: Simple Living in 1000 Square Feet or Less by Gerald Rowan is a nice book to give you some beginning ideas on building a small dwelling. There are 62 plan idea in the book, most of which are very unique. There are even a handful of designs that utilize shipping containers as a basis for the living space.
Even if none of the designs really strike your fancy the author discusses designing a compact cottage based on assembling modules (on paper first). Draw out squares on paper representing the sleeping area, kitchen/dining area, and living area. Then multiply each module to accommodate the number of people that will stay in the cabin. Maybe you need 2 sleeping areas, just one kitchen area, and 2 living areas. Then arrange and rearrange these squares to give you an idea of your final floor plan.
The only thing I didn’t care for with the book is the style of the pictures. It really reminds be of a 50’s Boy Scout manual or 50’s Popular Mechanics type of style. Not very cozy. But, if you grew up in that era this kind of artwork would probably be more appealing to you.
A chapter on more details of framing and construction would have been helpful, too.